Chapter 3 – AT Commands, S-Registers, and Results Codes

S-Registers

Certain modem values, or parameters, are stored in memory locations called S-registers. Use the S command to read or to alter the contents of S-Registers (see previous section).

Register Unit Range Default Description

Register

Unit

 

Range

Default

Description

S0

1 ring

 

0, 1–255

1

Sets the number of rings until the modem answers. ATS0=0

 

 

 

 

 

disables autoanswer completely.

S1

1 ring

 

0–255

0

Counts the rings that have occurred.

S2

decimal

 

0–127

43(+)

Sets ASCII code for the escape code character.

S3

decimal

 

0–127

13 (^M)

Sets ASCII code for the RETURN character.

S4

decimal

 

0–127

10 (^J)

Sets ASCII code for the LINE FEED character.

S5

decimal

 

0–127

8 (^H)

Sets ASCII code for the BACKSPACE character.

S6

1 sec.

 

2–255

2

Sets the time the modem will wait for a dial tone before aborting a

 

 

 

 

 

call.

S7

1 sec.

 

1–255

45

Sets the time the modem.

S8

1 sec.

 

0–255

2

Sets the length of a pause caused by a comma character in a

 

 

 

 

 

dialing command.

S9

100 ms

 

1–255

6

Sets delay between when the modem detects a valid carrier

 

 

 

 

 

signal and when it turns on its CD circuit.

S10

100 ms

 

1–254

7

Sets how long a carrier signal must be lost before the modem

 

 

 

 

 

disconnects. S10=255 causes the modem to not disconnect with

 

 

 

 

 

loss of carrier.

S11

1 ms

 

1–255

70

Sets spacing and duration of dialing tones. Recommended

 

 

 

 

 

minimum is 50 ms.

S13

decimal

 

0, 1–127

37 (%)

Sets ASCII code for remote configuration escape character.

 

 

 

 

 

S13=0 disables remote configuration.

S17

10 ms

 

1–255

25

Sets the length of the break time (space) sent to the local PC

 

 

 

 

 

when the modem receives a remote break.

S24

50 ms

 

0–255

20

Sets the time the DSR, CTS, and CD signals drop before going

 

 

 

 

 

high again. Used for some PBX and CBX phone systems.

S25

100 ms

 

0, 1–255

0

Sets the time the DTR signal must be dropped before the modem

 

 

 

 

 

disconnects. The 0 default equals 50 ms.

S30

1 min.

 

0, 1–255

0

Sets how long the modem waits after the last character is

 

 

 

 

 

received or transmitted before it disconnects. The 0 default

 

 

 

 

 

disables the timer.

S32

100 ms

 

0–255

20

Sets the time the modem will wait for a RETURN to be entered

 

 

 

 

 

during escape sequence execution.

S34

1 char

 

0–60

10

Sets the number of command characters allowed after +++AT.

S36

1 sec.

 

0, 1-255

5

Sets the time between DTR inactive and modem offhook. S36=0

 

 

 

 

 

disables DTR busy-out.

S37

1 sec.

 

0-255

5

Sets the time between DTR active and modem on-hook.

S43

decimal

 

28, 26,

0

Sets fixed V.34 connect speed. 28 = 28800 bps; 26 = 26400 bps;

 

 

 

24, 21,

 

48 = 4800 bps. 0 default disables this feature.

 

 

 

19, 16,

 

 

 

 

 

14, 12,

 

 

 

 

 

96, or 48

 

 

S48

decimal

 

33, 31,

0

Sets maximum V.34 connect speed. 33 = 33600 bps; 31 = 31200

 

 

 

28, 26,

 

bps;…48 = 4800 bps. 0 default disables feature (same as

 

 

 

24, 21,

 

S48=33).

 

 

 

19, 16,

 

 

 

 

 

14, 12,

 

 

 

 

 

96, or 48

 

 

Multi-Tech Systems, Inc. MT2834ZDX User's Guide

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Multi-Tech Systems MT2834ZDX manual Registers, Register Unit Range Default Description